MPs – including Flick Drummond (Portsmouth South), Alan Mak (Havant) and Suella Fernandes (Fareham) – had been under armed guard, with the Commons in lock down until just after 7pm.

Evacuated ministers and members of the public then gathered in Westminster Abbey.

Ms Fernandes said she was shocked by the afternoon’s drama but was quick to stress there was no detail on whether the incident was a terror attack.

Speaking to The News, she said: ‘A policeman has been stabbed on the estate. Another individual has been injured also. An air ambulance is here.

‘Now we have heard that a number of people have been hit by a car on Westminster Bridge.

‘It’s frightening and I get upset when I think about the policeman who has been stabbed.

‘The staff here have been on guard to protect members of the public and MPs here. They really do put their lives on the line.’

She added she expected to remain in Parliament for at least the next hour while police and emergency services secured the area.

Ms Fernandes said: ‘At first I didn’t believe what was happening. You see all these atrocious attacks in the news an you never think that it will happen on your doorstep.

‘I didn’t really believe it. I thought it was a joke or some kind of mistake.’

Mr Mak paid tribute to the swift response of police and parliamentary security staff for tackling the attacker.

‘This is very reassuring,’ he said. ‘They were very professional.’

Press Association reporter Laura Harding, who was in Westminster at the time of the incident, said: ‘Everyone has been evacuated into Central Lobby, including a group of schoolchildren and kitchen staff.

‘There are also a bunch of young people from the Hammersmith Boxing Club in their tracksuits and the British Lionhearts boxing group.’

Dennis Burns, who was just entering Parliament for a meeting when the security alert happened, said: ‘As I was coming through the doors at Portcullis House, a policeman grabbed someone who was coming in and threw him out.

‘As we were coming though the glass doors I was told by one security guard to get out while another one told me to get in.

‘As I walked in I heard a security guard get a radio message saying ‘a policeman has been stabbed’.

‘Then I walked in as police officers and security start rushing out of the front doors on to the street.

‘When I got inside I was wondering what the hell was going on and I saw dozens of panicked people running down the street. The first stream was around 30 people and the second stream was 70 people.